﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Demo
{
    class GetArea
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World");

            Console.WriteLine("请输入圆的半径");
            Double radius = Double.Parse(Console.ReadLine());
            Console.WriteLine("这个圆的面积为："+3.14*(radius*radius));
            Console.ReadKey();

        }
    }
}
